The findings suggested that night shifts suppress the production of 'sleep hormone' melatonin, which regulates the internal body clock (circadian rhythm).

New Delhi, June 27: Beware if you work in late night shifts, as according to a study, working at night may hinder your body’s ability to repair damaged DNA caused by normal cellular processes.

The findings suggested that night shifts suppress the production of ‘sleep hormone’ melatonin, which regulates the internal body clock (circadian rhythm).

They explained that the night shifts reduced the capacity to repair oxidative DNA damage due to insufficient levels of melatonin and may also result in cells harboring higher levels of DNA damage.

Over time, DNA damage that is not repaired will cause mutations that can lead to cancer.

Previous research on 223-night shift workers has shown that day sleep was associated with lower levels in their urine of a chemical by-product of active DNA tissue repair called 8-OH-dG than night sleep — potentially indicating the reduced capacity to repair cellular damage.

For the study, the team measured 8-OH-dG levels in the stored urine samples of 50-night shift workers from the previous study.

These 50 people had exhibited the widest discrepancies in levels of circulating melatonin between night work and night sleep.

Analysis of the urine samples showed that melatonin levels were much lower when taken during a night shift than when taken during a normal night’s sleep.

The researchers said explained that a particular pathway called NER is thought to be involved in the repair of DNA damage caused by oxygen free radicals, which are produced during normal cellular activity.

The research has shown that melatonin production boosts the activity of the genes involved in the NER pathway. They noted that relative to night sleep, reduced melatonin production among shift workers during night work is associated with significantly reduced urinary excretion of 8-OH-dG.

They added that if such effects are confirmed, melatonin supplementation should be explored as an intervention to reduce the occurrence of potentially carcinogenic DNA damage among shift workers.

The study is published in the Journal of Occupational and Environmental Medicine.